Planimeter.



lVi. VAN METER.

PLANIMETER.

APPLICATION FILED AUGJ ISHI. o Patented. Mar. 26, 1918. Z SHEET$-SHEETI.

M. VAN METER..

'PLANiMETER. APPLICATION FILED AUG-8.1917.-

2 SHEETS-SHEET 2.

R a M d m m Di MORTON VAN METER, 0F CADILLAC, MICHIGAN.

PLANIMETER.

Specification of Letters Patent. P a-tented IWaJr. 26, 191%.,

Application filed August 8, 1917. Serial No. 185,030.

To all 'wh0m it may concern Be it known that I, MORTON VAN METER, acitizen of the United States, residing at Cadillac, in the county ofVVeXford and State of Michigan, have invented certain new and usefulImprovements in Planimeters, of which the following i a specification.

This invention relates to improvements in planimeters and moreparticularly to an instrument of the rolling type in which the entireinstrument is rolled bodily over the surface of the board and thus canbe used to evaluate the area of extended figures such as cannot beaccomplished by the polar type planimeter without resetting.

One of the objects of my invention is to provide a planimeter of sturdy,rugged construction, capable of standing rough usage without injury andin which error due to wearing of its parts under long usage is.substantially negligible.

Another object of my invention is to provide such a planimeter which canbe manufactured at a comparatively small expense and yet will possess asmuch, if not greater accuracy than those commonly used.

Another object of my invention is to provide such a planimeter in whichno correction of reading is necessary in evaluating large areas asisrequired in using the polar type planimeter.

Still other and further objects will become readily apparent to thoseskilled in the art from a consideration of the following description anddrawings wherein Figure 1 is a plan view of my improved planimeter.

Fig. 2 is a vertical sectional view on the line 22 of Fig. 1, and;

Fig. 3 is a transverse vertical sectional view on the line 33 of Fig. 1.

In polar planimeters, as for example of the Amsler type, a pair ofpivoted arms are provided, the end of one arm being secured to the boardsurface and the end of the other arm provided with a tracing point foroutlining the configuration of the area to be measured. On the latterarm at the rear of the point of connection with the first arm, a recordwheel is provided which travels upon the surface of the board andindicates the area included within the outline traced.

One difficulty encountered in using a polar planlmeter is in having toaccount for the area of the zero circle when evaluating large areas andfurthermore it will be evident that when used on papers of glazedsurface there is always the likelihood of the record wheel giving anerroneous result through slippage in traveling over this mooth surfacehaving but slight tractive engagement with the wheel. In my improvedtype of planimeter this is eliminated by having the recording wheeltravel at all times upon the same surface, namely a conical roller, thusgiving a satisfactory and efficient tractive surface. In addition to theabove advantage it is possible to evaluate elongated areas, such forexample as occur in railroad grade indication drawings, which wouldrequire frequent resetting of the polar type planime ter. The rollertype planimeter such as I have evolved may be made to travel along agrade line of this character without resetting, giving at the end thedesired area reading.

In general the instrument comprises an open frame having front and rearbars 10 and 11 connected at the sides by side pieces 12-12, and 13-13offset and joined by short bars laparallel with the front and back bars.

In the area inclosed within the ends 13, 13, I have mounted a pair ofheavy traction wheels 15-15 upon a shaft 16 mounted t its end injournals 17 These large traction wheels provide the driving mechanismfor the planimeter, their motion being transmitted through a gear 18upon the shaft 16 to the pinion 19 carried upon the end of the cone 20against which the recording wheel travels. This cone is mounted at itsends in pivot bearings 21, set in brackets 22 secured at the junction ofthe side members 12 and 14. A shaft 23 parallel with the shaft 16 ispositioned between the side members 12, 12, carrying at its center asmall wheel 28 which serves a a third point of support for the frame.

The front member 10 is provided with a comparatively wide upper surface24 with a V-shaped longitudinal groove 25 extending across its frontedge portion and upon which the rollers 26 of the carriage indicated ingeneral by the numeral 27 rest. This carriage 27 is of U-shape having anupper legs 29, in which are pivoted, as'at 30, the ends of the tworollers 2626 which are of cylindrical form adapted to bear upon thesurface 24 and have at'their forward ends heads 31 of V-shaped crosssection for engagement with the groove 25. This carriage is transverselyslidable upon the front bar 10 and is provided at its front leg 29 withan outwardly extending bracket 32' carrying a pointed screw orpointer 33by means of which the outlines of the figure to be evaluated isoutlined. A record wheel carrying frame indicated in general at '34 hasa pair of U-shaped arms 35, the ends of which are provided with pivotbearings 36 for engagement with the carriage 27 at opposite ends of thetable 28. The U-shaped arms '35 are joined at their base 36 and at theopposite sides thereof-extend outwardly forming arms 37 within which therecord wheeliand its associated mechanism i mounted.

At the ends of the arms 37, 37 pivot bearings 38 are provided in whichthe record wheel shaft 39 is mounted. The record wheel "40 carried uponthe shaft 39 at one end portion thereof registers with a Vernier scale41 and at the other side of its midpoint isprovided with a'worm 42engaging with aworm wheel 43 carried on a shaft 44 which extendsoutwardly at right angles to the shaft 39 and carries on its upper end acounter wheel 46. The length of the bracket 34 is such as to positionthe record wheel 40 approximately on line with the axis of the cone'20,so that as the carriage 27 travels along the front frame member 10, therec- 0rd wheel 40'is moved upwardly or downwardly upon the coneaccording to the movement of the carriage.

In the particular embodiment which I I have illustrated the diameter ofthe driving wheels 15, the reduction of gearing between gear 18 andpinion 19, the pitch of the cone and the diameter of the record wheelare so proportioned and related that the indicating surface of therecordwheel is divided into five equal spaces each indicating a squareinch. The worm and worm wheel give a reduction of 1 to 20 so that thecounter wheel 46 is divided into 10 spaces each equivalent to ten squareinches.

' In the form illustrated the arrangement of the pivoted yoke in whichthe record wheel is mounted happens to be suchthat asit travels from oneend to the other of the frame member 10 the point of contact of theindicator wheel with the cone does not follow exactlyin a planeincluding the axis of the conical roller and a slight advancing orretarding of the record wheel is "caused as it is'moved along the coneindependent ofa'ny cone rotation. This error, however, it will be noted,is self correcting as any inwithout departing fromthe spirit of theinvention or the scope of the appended claims. Having described'myinvention, what I claim is r 1. A planimeter comprising a frame, *a

traction wheel, a cone driven by the tr'action wheel, a carriageslidable on the frame' on a line'parallelto the axis of the cone, afigure outlining pointer carried-by the carriage, and a record wheelmovable with the carriage and in'engagement withthe cone.

2. A planimeter comprising a frame, a pair of spaced aparttraction'wheels, cone pivoted in the frame on an axis parallel to theaxis of the traction wheels, gearsconnecting the cone and tractionwheels, a member movable on the carriage on a l ine parallel with theaxis of the traction wheels, a pointer carried by the memberand arecordwheel carried by the member and inengagementwith the surface of thecone.

3. A planimeter comprising a'frame, a pair of traction wheels, a cone,gears con necting the cone to the traction wheelsy-acarriage slidable ontheframe on-"a line parallel with the axis of the traction: wheels,

a record wheel carried by the carriage'with its axis of'rotationparallel with the axisof the cone and in engagement therewith, and

a-figure outlining pointerprojecting from the carriage.

4. A planimeter comprising a generally rectangular frame, a pair ofspaced apart traction wheels journaled within the frame, acone journaledin the frame, gears connecting the cone and traction wheels, asupporting roller journaled in the frame at' a point remote from thetraction wheels, a carriage slidable upon the frame'on a line parallelwith the axis of the tractionwhe'els, a figure outliningpoi'nterthereon; a" record wheel for engagement Wl'tlllth) cone, --andrecordwheel carrying frame pivotally con- 7 nected to the carriage.

5. A planimeter' comprising a fr ame, a

traction wheel, a cone, gearingconnecting the traction wheel and' cone,a carnage slid able on the frame on a line parallel with the axis of thecone, a record wheel engaging the upper side-of thecone, are'cord wheelsupporting frame, pivoted'to the carriage on an axis parallelwitlrthe'ax-is of 'the'rec 0rd wheel, and a pointer carried'by the "carria'ge.

i 6. A planim'eter comprising a "cone, a

frame in which the cone is mounted, means In testimony whereof Ihereunto set my for rotating the cone at a speed rate proporhand in thepresence of two subscribing 1O tional to the speed rate of framemovement, witnesses.

a carriage slidable upon the frame, on an 5 axis parallel with the axisof the cone, a MORTON VAN METER figure outlining pointer on thecarriage, and In the presence of-- a record wheel carried by thecarriage and. ESTHER E. VAN METER, in engagement with the surface of thecone. 0. W. CUNNINGHAM.

copies of this patent may be obtained for five cents each, by addressingthe Commissioner 01? JPutentu,

- Washington, D. C.

